1. Field of the Invention
The present invention relates to an electronic component including an electronic element and a substrate on which the electronic element is mounted.
2. Description of the Related Art
In recent years, the sizes and heights of electronic components including electronic elements and substrates on which the electronic elements are mounted have been increasingly reduced. In such situations, a process in which a predetermined surface of an electronic element and that of a substrate are mechanically or electrically connected to each other by electrically conductive bumps, the so-called flip-chip process, is often used.
FIGS. 1A and B are respective different longitudinal cross sectional views of an electronic component 10 using a generally-used flip-chip process of the related art. As shown in FIGS. 1A and B, the electronic component 10 includes an electronic element 20 and a substrate 30 onto which the electronic element 20 is mounted.
As shown in FIG. 1A, a predetermined functional surface 120 of the electronic element 20 is positioned so as to face in a particular direction (downwards in FIG. 1A), and is opposed to a predetermined mount surface 130 of the substrate 30. The electronic element 20 and the substrate 30 are connected to each other electrically and mechanically by metallic bumps 40 interposed between them. Moreover, as shown in FIG. 1B, to strengthen the connection, a method of filling a resin 90 between the electronic element 20 and the substrate 30 is generally known, for example, in the semiconductor device field and so forth. The resin 90 used for the above-described purpose is generally called an under-fill.
However, in the case of electronic components in which electrodes or the like are provided on the functional surfaces of electronic elements such as surface acoustic wave elements, and the functions of the elements cannot sufficiently be achieved if a resin adheres to the functional surfaces, the under-fill cannot be applied. Accordingly, the electronic elements are mechanically connected to the mount surfaces of the substrates by the bumps only. If the total contact-area of the bumps based on the mass of an electronic element is small, problems will arise in that the electronic element is released or separated from the bumps, due to external mechanical loads caused by falling, vibration, and other conditions, and the functions of the electronic component itself are deteriorated.
In order to overcome the problems described above, preferred embodiments of the present invention provide an electronic component in which an electronic element and a substrate can be mechanically bonded to each other with sufficient strength.
According to a preferred embodiment of the present invention, an electronic component of the present invention includes an electronic element and a substrate to which the electronic element is mounted, the electronic element and the substrate being electrically or mechanically connected to each other by at least three bumps, wherein both the value obtained by dividing the total bonding-area of the at least three bumps bonded to the electronic element by the mass of the electronic element and the value obtained by dividing the total bonding-area of the at least three bumps bonded to the substrate by the mass of the electronic element are at least about 8.8 mm2/g.
It is preferable and advantageous if both the value obtained by dividing the total bonding-area of the bumps bonded to the electronic element by the mass of the electronic element and the value obtained by dividing the total bonding-area of the bumps bonded to the substrate by the mass of the electronic element are at least about 11.6 mm2/g.
Moreover, the electronic component of preferred embodiments of the present invention is preferably characterized in that the bumps are made of Au or an alloy including Au as a major component.
Furthermore, it is preferred that the electronic component of the present invention is constructed such that the electronic element and the substrate are mechanically connected to each other by the bumps only.
Also, in the electronic component of preferred embodiments of the present invention, the electronic element may be a surface acoustic wave element including at least one IDT electrode disposed on a piezoelectric substrate.
According to the electronic component of preferred embodiments of the present invention, mechanical bonding at a sufficient strength can be achieved even for a surface acoustic wave device as the electronic component including a surface acoustic wave element in which an under-fill cannot be used for bonding of the electronic element to a substrate.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments with reference to the attached drawings.